Hydrolytic stability is a physical characteristic commonly sought in polymers. It is therefore desirable to find methods for providing polymer compositions with greater hydrolytic stability and that are less detrimental to process equipment.
U.S. Pat. No. 4,619,956 discloses the combination of 2,2,6,6-tetraalkylpiperidine hindered amine light stabilizers (HALS) and/or their addition salts with triazine ultraviolet absorbers for stabilizing thermoset acrylic and alkyd coatings. U.S. Pat. No. 5,714,530 discloses the utility of combining non-polymeric 2,2,6,6,-tetraalkylpiperidine HALS salts and/or their acid addition salts with triazine ultraviolet light absorbers for stabilizing certain polymer compositions. U.S. Pat. No. 6,051,164 discloses the use of a polymer stabilizing system comprising from about 50 to about 5,000 ppm of at least one ortho hydroxyl tris-aryl triazine light absorber and from about 500 ppm to about 1.25 percent of at least one oligomer, polymeric or high molecular weight HALS having a molecular weight of at least about 500, wherein the weight ratio of HALS to triazine light absorber is from about 3:1 to about 20:1.
The detrimental effect of phosphorus-containing additives on the hydrolytic stability of polycarbonate and polycarbonate-polyester blends is disclosed in U.S. Pat. Nos. 4,456,717, 5,354,791, 5,744,526, 6,103,796, 4,393,158, and 6,107,375. Improved hydrolytic stability for polycarbonates stabilized with phosphorus-containing compounds and siloxanes containing oxetane groups are disclosed in U.S. Pat. No. 4,456,717. Improved hydrolytic stability for polycarbonates stabilized with phosphorus-containing compounds and an oligomer or polymer containing at least one pendant cyclic iminoether group per molecule is disclosed in U.S. Pat. No. 6,107,375. Improved hydrolytic stability for polycarbonates stabilized with phosphorus-containing compounds and an epoxy compound is disclosed in U.S. Pat. No. 4,393,158. Improved hydrolytic stability for polycarbonate-polyester blends stabilized with phosphorus-containing compounds and a polyester having epoxy functionality is disclosed in U.S. Pat. No. 5,354,791. Improved hydrolytic stability for polycarbonates stabilized with phosphorus-containing compounds and hexamethylene tetra amine is disclosed in U.S. Pat. No. 5,744,526. Specifically, U.S. Pat. No. 5,744,526 teaches the addition of the amine to stabilize the phosphite against hydrolysis and consequently improving the hydrolytic stability of the polycarbonate composition.
This present invention relates to polycarbonates and the unexpected improvements in hydrolytic stability for polycarbonates containing an acidic phosphorous compound and a hindered amine light stabilizers (HALS).